Long/random-wire balun and grounding Q (longish)
 

I've got a little shortwave receiver that has a decent amount of gain in
it's antenna input. I've been experimenting with different lengths and
placements of the wire, and seen some interesting homebrew antennas I
might try once the snow melts.

I know that receivers are less demanding of impedance matching in
general, but my readings suggest that I should have a balun (unun) of
some sort to match the impedance better, since I'm pretty much stuck
with end-fed longwires. This should get more signal to my front-end,
and a proper shielded connection to my receiver should help minimize
stray RF noise.

I'm a renter, so I'm going to experiment with running a wire along the
eaves on the balcony, which is open to two sides of the house (wooden
two-story.) That is, I do not have the luxury of using the yard, trees
or anything.

So, my idea is to have a long wire (or folded longwire made from a
length of twin-lead) go to a balun (or unun, since this is really
unbalanced-to-unbalanced) and then run a downwire from there to my
receiver through a window.

I'm guessing the real advantage would be realized if I had a good RF
ground at the receiver and/or balun. This will be sort of tricky. I
don't even think I have copper cold-water pipes anywhere, and running
copper braid over the balcony, down the side of the building and into
6-foot rod just ain't going to happen. I've heard of people using
houseplants for poor grounds when no other was available, and I have
many kilos of wet earth on the balcony.

I've seen a neat artificial ground/antenna tuner from MFJ (I think)
which seems to offer a lot of bang for the buck. It even has multiple
inputs for high-Z single wires. Would this be useful for SW?

Finally, I'm probably just going to wind my own balun out of a ferrite
core. I just can't seem to find the details on how to wind the copper.
Do I wind the primary first around the whole core, and then the
secondary on top of it? Sorry if this is stupid question, but I've got
most of the math figured out (i.e., no. of turns and such) but since
I've never seen a balun... my assumption (right or wrong) is that it is
just a special transformer.

Thanks for your comments.

-- cm

On Wed, 02 Mar 2005 13:04:50 -0500, clvrmnky
wrote:

I know that receivers are less demanding of impedance matching in
general, but my readings suggest that I should have a balun (unun) of
some sort to match the impedance better, since I'm pretty much stuck
with end-fed longwires.

Hi OM,

This match, as you speak of, is probably remote from any probability
you are likely to encounter with the antenna options you describe in
your posting. However, there are other merits:

a proper shielded connection to my receiver should help minimize
stray RF noise.

Presuming you mean to terminate the far end shield connection to
ground.

I'm guessing the real advantage would be realized if I had a good RF
ground at the receiver and/or balun. This will be sort of tricky. I
don't even think I have copper cold-water pipes anywhere, and running
copper braid over the balcony, down the side of the building and into
6-foot rod just ain't going to happen.

OK, so we strike out those as options not available to you.

I've heard of people using
houseplants for poor grounds when no other was available, and I have
many kilos of wet earth on the balcony.

Don't even think of it. Ground does not mean wet mud.

I've seen a neat artificial ground/antenna tuner from MFJ (I think)
which seems to offer a lot of bang for the buck. It even has multiple
inputs for high-Z single wires. Would this be useful for SW?

Certainly, but you would achieve just as much with a simple tuner
(cheap one without the transmitter meters). In fact, this tuner is
generally very necessary to keep local AM stations from desensitizing
your receiver. This is a common plight suffered by many who would
otherwise think they were doing pretty well, but just need more
antenna to get those signals others are reporting.

Finally, I'm probably just going to wind my own balun out of a ferrite
core. I just can't seem to find the details on how to wind the copper.
Do I wind the primary first around the whole core, and then the
secondary on top of it?

What you are describing is a conventional power transformer - NOT the
same thing as a Transmission Line Transformer. What you should really
concentrate on is what is called a Transmission Line Choke (perfectly
accomplished using a 1:1 Current BalUn/UnUn).

73's
Richard Clark, KB7QHC

Try this simple test.

Tune your receiver to a part of the dial where there's no station.
Disconnect the antenna from your receiver. If the noise level drops,
impedance matching won't help your signal/noise ratio, it'll just make
everything louder. You can accomplish the same thing by turning up the
volume control.

Roy Lewallen, W7EL

clvrmnky wrote:
I've got a little shortwave receiver that has a decent amount of gain in
it's antenna input. I've been experimenting with different lengths and
placements of the wire, and seen some interesting homebrew antennas I
might try once the snow melts.

I know that receivers are less demanding of impedance matching in
general, but my readings suggest that I should have a balun (unun) of
some sort to match the impedance better, since I'm pretty much stuck
with end-fed longwires. This should get more signal to my front-end,
and a proper shielded connection to my receiver should help minimize
stray RF noise.

I'm a renter, so I'm going to experiment with running a wire along the
eaves on the balcony, which is open to two sides of the house (wooden
two-story.) That is, I do not have the luxury of using the yard, trees
or anything.

So, my idea is to have a long wire (or folded longwire made from a
length of twin-lead) go to a balun (or unun, since this is really
unbalanced-to-unbalanced) and then run a downwire from there to my
receiver through a window.

I'm guessing the real advantage would be realized if I had a good RF
ground at the receiver and/or balun. This will be sort of tricky. I
don't even think I have copper cold-water pipes anywhere, and running
copper braid over the balcony, down the side of the building and into
6-foot rod just ain't going to happen. I've heard of people using
houseplants for poor grounds when no other was available, and I have
many kilos of wet earth on the balcony.

I've seen a neat artificial ground/antenna tuner from MFJ (I think)
which seems to offer a lot of bang for the buck. It even has multiple
inputs for high-Z single wires. Would this be useful for SW?

Finally, I'm probably just going to wind my own balun out of a ferrite
core. I just can't seem to find the details on how to wind the copper.
Do I wind the primary first around the whole core, and then the
secondary on top of it? Sorry if this is stupid question, but I've got
most of the math figured out (i.e., no. of turns and such) but since
I've never seen a balun... my assumption (right or wrong) is that it is
just a special transformer.

Thanks for your comments.

-- cm

The answers you get on this group are likely to be far less than useful. I
would recommend rec.radio.shortwave.

"clvrmnky" wrote in message
...
I've got a little shortwave receiver that has a decent amount of gain in
it's antenna input. I've been experimenting with different lengths and
placements of the wire, and seen some interesting homebrew antennas I
might try once the snow melts.

I know that receivers are less demanding of impedance matching in
general, but my readings suggest that I should have a balun (unun) of
some sort to match the impedance better, since I'm pretty much stuck
with end-fed longwires. This should get more signal to my front-end,
and a proper shielded connection to my receiver should help minimize
stray RF noise.

I'm a renter, so I'm going to experiment with running a wire along the
eaves on the balcony, which is open to two sides of the house (wooden
two-story.) That is, I do not have the luxury of using the yard, trees
or anything.

So, my idea is to have a long wire (or folded longwire made from a
length of twin-lead) go to a balun (or unun, since this is really
unbalanced-to-unbalanced) and then run a downwire from there to my
receiver through a window.

I'm guessing the real advantage would be realized if I had a good RF
ground at the receiver and/or balun. This will be sort of tricky. I
don't even think I have copper cold-water pipes anywhere, and running
copper braid over the balcony, down the side of the building and into
6-foot rod just ain't going to happen. I've heard of people using
houseplants for poor grounds when no other was available, and I have
many kilos of wet earth on the balcony.

I've seen a neat artificial ground/antenna tuner from MFJ (I think)
which seems to offer a lot of bang for the buck. It even has multiple
inputs for high-Z single wires. Would this be useful for SW?

Finally, I'm probably just going to wind my own balun out of a ferrite
core. I just can't seem to find the details on how to wind the copper.
Do I wind the primary first around the whole core, and then the
secondary on top of it? Sorry if this is stupid question, but I've got
most of the math figured out (i.e., no. of turns and such) but since
I've never seen a balun... my assumption (right or wrong) is that it is
just a special transformer.

Thanks for your comments.

-- cm

Classic. I new someone would come up with the "stick a coat hanger in your
antenna socket and be happy" line.

"Roy Lewallen" wrote in message
...
Try this simple test.

Tune your receiver to a part of the dial where there's no station.
Disconnect the antenna from your receiver. If the noise level drops,
impedance matching won't help your signal/noise ratio, it'll just make
everything louder. You can accomplish the same thing by turning up the
volume control.

Roy Lewallen, W7EL

clvrmnky wrote:
I've got a little shortwave receiver that has a decent amount of gain in
it's antenna input. I've been experimenting with different lengths and
placements of the wire, and seen some interesting homebrew antennas I
might try once the snow melts.

I know that receivers are less demanding of impedance matching in
general, but my readings suggest that I should have a balun (unun) of
some sort to match the impedance better, since I'm pretty much stuck
with end-fed longwires. This should get more signal to my front-end,
and a proper shielded connection to my receiver should help minimize
stray RF noise.

I'm a renter, so I'm going to experiment with running a wire along the
eaves on the balcony, which is open to two sides of the house (wooden
two-story.) That is, I do not have the luxury of using the yard, trees
or anything.

So, my idea is to have a long wire (or folded longwire made from a
length of twin-lead) go to a balun (or unun, since this is really
unbalanced-to-unbalanced) and then run a downwire from there to my
receiver through a window.

I'm guessing the real advantage would be realized if I had a good RF
ground at the receiver and/or balun. This will be sort of tricky. I
don't even think I have copper cold-water pipes anywhere, and running
copper braid over the balcony, down the side of the building and into
6-foot rod just ain't going to happen. I've heard of people using
houseplants for poor grounds when no other was available, and I have
many kilos of wet earth on the balcony.

I've seen a neat artificial ground/antenna tuner from MFJ (I think)
which seems to offer a lot of bang for the buck. It even has multiple
inputs for high-Z single wires. Would this be useful for SW?

Finally, I'm probably just going to wind my own balun out of a ferrite
core. I just can't seem to find the details on how to wind the copper.
Do I wind the primary first around the whole core, and then the
secondary on top of it? Sorry if this is stupid question, but I've got
most of the math figured out (i.e., no. of turns and such) but since
I've never seen a balun... my assumption (right or wrong) is that it is
just a special transformer.

Thanks for your comments.

-- cm

Do you believe that what I posted isn't true, or do you just wish it
isn't true?

Roy Lewallen, W7EL

CW wrote:
Classic. I new someone would come up with the "stick a coat hanger in your
antenna socket and be happy" line.

"Roy Lewallen" wrote in message
...

Try this simple test.

Tune your receiver to a part of the dial where there's no station.
Disconnect the antenna from your receiver. If the noise level drops,
impedance matching won't help your signal/noise ratio, it'll just make
everything louder. You can accomplish the same thing by turning up the
volume control.

Roy Lewallen, W7EL

On Fri, 4 Mar 2005 21:30:40 -0800, "CW" wrote:

Classic. I new someone would come up with the "stick a coat hanger in your
antenna socket and be happy" line.

As a rule I subscribe to the school that says every antenna should be
well-matched, in the clear and fed with low loss line, even those used
for receiving. Must come from my VHF/DXing background.

That said, I know my friend Roy is correct and I am wrong when he
gives this advice. Generally speaking, the SNR is set at the antenna
and nothing done after that will make much difference. This isn't
always the case if there are noise sources that can nulled or reduced
by phasing or other directive techniques that don't reduce the signal
simultaneously.

Roy did not mention this at all. He spoke to "impedance matching."

Wes N7WS

ps. You have no idea how hard it is to type with one (the "wrong")
hand while doing drugs. I had 2 1/2 hours of surgery putting my rt.
shoulder together on Thursday. Just in time to keep me out of the DX
contest---good planning :(



"Roy Lewallen" wrote in message
...
Try this simple test.

Tune your receiver to a part of the dial where there's no station.
Disconnect the antenna from your receiver. If the noise level drops,
impedance matching won't help your signal/noise ratio, it'll just make
everything louder. You can accomplish the same thing by turning up the
volume control.

Roy Lewallen, W7EL
[snip]

On Sat, 05 Mar 2005 06:18:45 -0700, Wes Stewart
wrote:

ps. You have no idea how hard it is to type with one (the "wrong")
hand while doing drugs. I had 2 1/2 hours of surgery putting my rt.
shoulder together on Thursday. Just in time to keep me out of the DX
contest---good planning :(


Hi Wes,

I don't think this will boost your spirits by more than one S-Unit,
but in today's NYT there was a report of a fellow that chopped off
both hands, and had them sewn back on.
graphic:
http://graphics8.nytimes.com/images/...n/05hands2.jpg
story:
http://www.nytimes.com/2005/03/05/nyregion/05hands.html

73's
Richard Clark, KB7QHC

On Sat, 05 Mar 2005 11:48:01 -0800, Richard Clark
wrote:

On Sat, 05 Mar 2005 06:18:45 -0700, Wes Stewart
wrote:

ps. You have no idea how hard it is to type with one (the "wrong")
hand while doing drugs. I had 2 1/2 hours of surgery putting my rt.
shoulder together on Thursday. Just in time to keep me out of the DX
contest---good planning :(


Hi Wes,

I don't think this will boost your spirits by more than one S-Unit,
but in today's NYT there was a report of a fellow that chopped off
both hands, and had them sewn back on.
graphic:
http://graphics8.nytimes.com/images/...n/05hands2.jpg
story:
http://www.nytimes.com/2005/03/05/nyregion/05hands.html

Oh my, that's gotta hurt.

Some years ago my wife had hand surgery and afterwards was getting
physical therapy. Another patient there had lost a thumb to a
circular saw. They made him a new one out of another finger.

On Sat, 05 Mar 2005 13:19:40 -0700, Wes Stewart
wrote:

On Sat, 05 Mar 2005 11:48:01 -0800, Richard Clark
wrote:

On Sat, 05 Mar 2005 06:18:45 -0700, Wes Stewart
wrote:

ps. You have no idea how hard it is to type with one (the "wrong")
hand while doing drugs. I had 2 1/2 hours of surgery putting my rt.
shoulder together on Thursday. Just in time to keep me out of the DX
contest---good planning :(


Hi Wes,

I don't think this will boost your spirits by more than one S-Unit,
but in today's NYT there was a report of a fellow that chopped off
both hands, and had them sewn back on.
graphic:
http://graphics8.nytimes.com/images/...n/05hands2.jpg
story:
http://www.nytimes.com/2005/03/05/nyregion/05hands.html

Oh my, that's gotta hurt.

Last week in the news some lady got mad at her man and cut his
ying-yang off and flushed down the toilet. It was later recovered,
taken to the hospital, cleaned up and sewn back on the man.

Now that would hurt...

Bob
k5qwg



Some years ago my wife had hand surgery and afterwards was getting
physical therapy. Another patient there had lost a thumb to a
circular saw. They made him a new one out of another finger.

On Sat, 05 Mar 2005 23:39:44 GMT, Bob Miller
wrote:

Now that would hurt...

There you go Wes. Do you feel any better now? G


Danny, K6MHE

Wes Stewart wrote:
Some years ago my wife had hand surgery and afterwards was getting
physical therapy. Another patient there had lost a thumb to a
circular saw. They made him a new one out of another finger.

I saw on TV the other day where they made a guy
a new thumb from one of his toes.
--
73, Cecil http://www.qsl.net/w5dxp


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CW wrote:
The answers you get on this group are likely to be far less than
useful. I
would recommend rec.radio.shortwave.

CW, I would suggest you refresh yourself on Signal-to-Noise Ratio, and
what it has to do with antennas. I took a look at the shortwave group,
and found a lot of garbage with little or no technical content. This
thread has had some excellent content, care to explain why it was far
less than useful?

On 02/03/2005 6:25 PM, Richard Clark wrote:
On Wed, 02 Mar 2005 13:04:50 -0500, clvrmnky
wrote:
[...]
I've seen a neat artificial ground/antenna tuner from MFJ (I think)
which seems to offer a lot of bang for the buck. It even has multiple
inputs for high-Z single wires. Would this be useful for SW?

Certainly, but you would achieve just as much with a simple tuner
(cheap one without the transmitter meters). In fact, this tuner is
generally very necessary to keep local AM stations from desensitizing
your receiver. This is a common plight suffered by many who would
otherwise think they were doing pretty well, but just need more
antenna to get those signals others are reporting.

I've been looking more seriously at the balun/tuner/ground offerings out
there. Seems to be a fair amount of contention out there about whether
antenna tuners work for SW.

If I can lessen the abuse my otherwise sensitive front-end is taking
from the wire, then maybe it's worth a try. That is, I'm
hoping/guessing that such a device will help my radio not hear a strong
signal 10-15kHz on either side of the mark, swamping out stuff I might
otherwise hear near these stations.

In this regard, homebrew is good because it allows me to experiment for
cheap. Even the cheapest MFJ equipment is a bit steep shipped to my
door in Canada.


Finally, I'm probably just going to wind my own balun out of a ferrite
core. I just can't seem to find the details on how to wind the copper.
Do I wind the primary first around the whole core, and then the
secondary on top of it?

What you are describing is a conventional power transformer - NOT the
same thing as a Transmission Line Transformer. What you should really
concentrate on is what is called a Transmission Line Choke (perfectly
accomplished using a 1:1 Current BalUn/UnUn).

Hmmm. I understand that a balun is really a type of matching
transformer, and that the specific nomenclature used is really just to
distinguish the various use, application and materials of the transformer.

All the designs for homebrew longwire X:1 baluns I've seen are step-down
transformers using specific types of ferrite material. Of course,
typical use often has one side of the primary and secondary going to a
good RF ground (for balanced application, anyway), which I do not have.

My thinking is that since I'm going to be experimenting with different
wire antennas this summer, why not try a few different matching
techniques as well?

The lack of good RF ground is going to be a challenge, and may preclude
any of this. I've got lots of wire, however, so I'm willing to give a
weekends up to try different things.

-- cm

On 02/03/2005 8:57 PM, Roy Lewallen wrote:
Try this simple test.

Tune your receiver to a part of the dial where there's no station.
Disconnect the antenna from your receiver. If the noise level drops,
impedance matching won't help your signal/noise ratio, it'll just make
everything louder. You can accomplish the same thing by turning up the
volume control.

Pulling the wire just attenuates the noise. So, a more balanced match
will not help with selectivity or overworked front-ends?

If this is the case, and a balun is most useful for transmitters trying
to manage SWR, then I guess it doesn't matter.

I'm still hoping that keeping all of the antenna outside may help with
household EMI. I sort of though that since I'm bothering to have a
transmission line, I may as well hack together a matching circuit for
efficiency.

On 10/03/2005 12:31 PM, clvrmnky wrote:
On 02/03/2005 8:57 PM, Roy Lewallen wrote:

Try this simple test.

Tune your receiver to a part of the dial where there's no station.
Disconnect the antenna from your receiver. If the noise level drops,
impedance matching won't help your signal/noise ratio, it'll just make
everything louder. You can accomplish the same thing by turning up the
volume control.

Pulling the wire just attenuates the noise. So, a more balanced match
will not help with selectivity or overworked front-ends?

If this is the case, and a balun is most useful for transmitters trying
to manage SWR, then I guess it doesn't matter.

.... in which case my only real choice is to shorten the antenna, or
attenuate the signal coming to my front-end a little ...

Hmmm. More to think about.

clvrmnky wrote:
The lack of good RF ground is going to be a challenge, and may preclude
any of this.

If you use a balanced antenna system, you don't need
an RF ground for the receive function.
--
73, Cecil, W5DXP


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On Thu, 10 Mar 2005 12:24:15 -0500, clvrmnky
wrote:
I've been looking more seriously at the balun/tuner/ground offerings out
there. Seems to be a fair amount of contention out there about whether
antenna tuners work for SW.

Hi OM,

I am sure that is the gospel in rec.radio.shortwave. There is little
there that qualifies as dependable information - except what station
was being heard (and then, this information is obviously iffy).

If I can lessen the abuse my otherwise sensitive front-end is taking
from the wire, then maybe it's worth a try. That is, I'm
hoping/guessing that such a device will help my radio not hear a strong
signal 10-15kHz on either side of the mark, swamping out stuff I might
otherwise hear near these stations.

No, no tuner is going to have that much Q unless you get a very small
loop to go with it. Then, you are better off tuning the loop instead.
All-in-all you need to twist a knob somewhere. There are several
merits of using tuners with longwires. The chief among them is that a
tuner will depress the strenght of local AM stations that will desense
your receiver (even if you are not even tuned anywhere near that AM
station's frequency - such is its power and the weakness of receiver
front ends).

In this regard, homebrew is good because it allows me to experiment for
cheap.

By all means, do it.

Hmmm. I understand that a balun is really a type of matching
transformer, and that the specific nomenclature used is really just to
distinguish the various use, application and materials of the transformer.

This is all true, but bears very little on your needs.

All the designs for homebrew longwire X:1 baluns I've seen are step-down
transformers using specific types of ferrite material.

Those are conventional transformers, not chokes, not BalUns (or
UnUns).

Of course,
typical use often has one side of the primary and secondary going to a
good RF ground (for balanced application, anyway), which I do not have.

May as well divorce yourself from those explanations. A tuner will do
the job of transforming AND filter out the crap. A tuner is a
variable transformer. If you have a single wire coming in to the
tuner, add a hank of wire to the tuner's ground connection [hank = 20'
±6dB].

My thinking is that since I'm going to be experimenting with different
wire antennas this summer, why not try a few different matching
techniques as well?

Matching at the antenna, or matching at the receiver? Unless you have
long arms, or many antennas for each band, it is simpler to match at
the receiver.

The lack of good RF ground is going to be a challenge, and may preclude
any of this. I've got lots of wire, however, so I'm willing to give a
weekends up to try different things.

Returning to the need for a BalUn, properly a choke, for your
application. It is useful for reducing house noise from getting mixed
with your signal. Conventional transformers won't do that (unless you
add a choke at their output on the signal downstream).

73's
Richard Clark, KB7QHC

clvrmnky wrote:
On 10/03/2005 12:31 PM, clvrmnky wrote:

On 02/03/2005 8:57 PM, Roy Lewallen wrote:

Try this simple test.

Tune your receiver to a part of the dial where there's no station.
Disconnect the antenna from your receiver. If the noise level drops,
impedance matching won't help your signal/noise ratio, it'll just
make everything louder. You can accomplish the same thing by turning
up the volume control.

Pulling the wire just attenuates the noise. So, a more balanced match
will not help with selectivity or overworked front-ends?

If this is the case, and a balun is most useful for transmitters
trying to manage SWR, then I guess it doesn't matter.

... in which case my only real choice is to shorten the antenna, or
attenuate the signal coming to my front-end a little ...

Hmmm. More to think about.

You're on the right track, but more information might help.

Your antenna is picking up signal and noise. When you disconnect your
antenna, the antenna's signal and noise are removed, leaving only the
receiver's internal noise. The fact that the noise dropped means that
the noise being coming into the receiver from the antenna is larger than
the internal receiver noise. This is nearly always the case at HF and
nearly never the case at VHF and higher. As long as the noise from the
antenna dominates over the receiver noise, then improving the impedance
match, which is what the original question and answer were about, will
only make both the signal and noise (both coming from the antenna)
bigger. This is exactly what you get when you increase the volume, and
doesn't help the signal to noise ratio one bit. It therefore doesn't
help you hear signals.

There are other ways to help the signal to noise ratio, though. If a
signficant amount of the noise is originating locally, improving
feedline balance with a balun might help. Horizontal polarization will
often be less sensitive than vertical to moderately local noise sources,
because vertically polarized waves can propagate by surface waves while
horizontally polarized waves can't. Feedline balance also improves
rejection of vertically polarized waves when the antenna is horizontal.
This is because it prevents pickup from the feedline itself, which is
often partially, at least, vertical.

Increased antenna directivity will help if the signal and noise are
coming from different directions. But this requires a mechanically or
electrically rotatable antenna unless you're only interested in
listening in certain directions. Short wave listeners sometimes use a
small rotatable loop, which has sharp nulls which can be pointed toward
a single dominant noise source.

You mention an "overworked" front end. If your front end is getting
overloaded from strong signals, which usually manifests itself as
cross-modulation -- "ghost" signals created from existing signals at
different frequencies -- either a passive preselector or an attenuator
is needed. The former is better only if the loud signals are on
frequencies reasonably removed from the frequency where you're
listening. Adding attenuation is fine, until you add so much that the
receiver noise begins dominating. You can use the antenna-disconnection
test to check for that condition. Another way to attenuate the signal is
to *degrade* the impedance match. That's right, if overload is the
problem, you'll do better with a lousier match.

You also mention selectivity. A preselector can take care of attenuating
strong, out-of-band signals. But nothing you can practically do outside
the receiver will help you separate two signals which are close
together. That requires internal modification to the receiver.

Forget about SWR. It's not of any use in improving your ability to hear
signals at HF where the noise from the antenna dominates.

Roy Lewallen, W7EL

clvrmnky wrote:
. . .

Hmmm. I understand that a balun is really a type of matching
transformer, and that the specific nomenclature used is really just to
distinguish the various use, application and materials of the transformer.


No, that's not correct. Balun is a contraction of "balanced-unbalanced".
A balun is sometimes combined with a transformer or made to transform
impedance, and sometimes it isn't. Its function is to balance the
currents on the two feedline conductors (either coax or parallel wire
line) to prevent radiation from the line when transmitting and pickup
from the line when receiving. The impedance transformation is a separate
function for a different purpose.

All the designs for homebrew longwire X:1 baluns I've seen are step-down
transformers using specific types of ferrite material. Of course,
typical use often has one side of the primary and secondary going to a
good RF ground (for balanced application, anyway), which I do not have.

A typical 1:1 "current" or "choke" balun, which does what I described
above, does not require any external "ground" or other connection. If
fact, such a connection provides a path for imbalance current and can
actually degrade balance. There are a number of ways of providing this
function, with and without ferrite cores.

My thinking is that since I'm going to be experimenting with different
wire antennas this summer, why not try a few different matching
techniques as well?

There's no reason not to experiment. Improving the match won't help your
signal-to-noise ratio. After your experiments show that this is so, you
can go back and learn why not.


The lack of good RF ground is going to be a challenge, and may preclude
any of this. I've got lots of wire, however, so I'm willing to give a
weekends up to try different things.

There's no need for an RF ground if you use a well-balanced antenna.

Roy Lewallen, W7EL

On 10/03/2005 1:04 PM, Cecil Moore wrote:
clvrmnky wrote:

The lack of good RF ground is going to be a challenge, and may
preclude any of this.


If you use a balanced antenna system, you don't need
an RF ground for the receive function.

Hmmm. I can probably make a decent-sized folded dipole out on the
patio. It will have to turn a corner, but I can probably get a
fair-sized loop out there.

On 10/03/2005 4:15 PM, clvrmnky wrote:
On 10/03/2005 1:04 PM, Cecil Moore wrote:

clvrmnky wrote:

The lack of good RF ground is going to be a challenge, and may
preclude any of this.



If you use a balanced antenna system, you don't need
an RF ground for the receive function.


Hmmm. I can probably make a decent-sized folded dipole out on the
patio. It will have to turn a corner, but I can probably get a
fair-sized loop out there.

Ok, further to this. Even if I'm not to care about impedance matching
or choking, my receiver has an unbalanced antenna input. One side of
the antenna connection simply goes to "chassis" ground.

This implies that I should use a traditional BalUn to make the balance
connection work for me. Otherwise, one side of a dipole or looped
longwire is just going to go straight to ground (such as it is.)

I built myself a reasonably stealthy random-wire running along the top
of my wooden balcony railing (which turns a 90-deg corner around the
building) for a total length of around 25-30 ft. I was considering
simply looping the wire to make a bent, untuned, "folded dipole" (the
wires would be 5-6 inches apart) just to get more wire into the wind.

To realize this, I am supposing I'll have to use a true BalUn to get the
signal into my unbalanced front-end somehow. Since most designs for a
true BalUn assumes I have a decent ground, I'm a bit stumped by your
comment. Perhaps the ground of the BalUn can just go to the coax sleeve?

Thanks for all your suggestions.

On Mon, 14 Mar 2005 13:02:20 -0500, clvrmnky
wrote:
This implies that I should use a traditional BalUn to make the balance
connection work for me. Otherwise, one side of a dipole or looped
longwire is just going to go straight to ground (such as it is.)

Hi OM,

You reject the BalUn (matching/choking) to only presume the
implication (one wire goes to ground) forces you to use it for another
reason?

Wrong implication, even if the solution works. The one side of any
dipole/loop antenna design going "straight to ground" (ground a
euphemism for Hell?) is not a loss in any sense of the design. The
receiver is sharing the same path - unless it is strictly battery
operated without a charger connection.

Your radio wants to see a signal potential applied across its input
and chassis (as you put it, which is suitable enough). With a
monopole the input is satisfied, but you need either a ground or
counterpoise connected to the chassis. With a dipole or loop, the two
returning wires meet the radio's needs at the input/chassis
connection. A ground connection or counterpoise for the dipole/loop
would be benign in the practical sense. You won't need it (unless you
have lightning phobias); and with the common specie of radio you will
have it, somewhere, anyway (it will then simply be uncontrolled and
variable).

Perhaps the ground of the BalUn can just go to the coax sleeve?

That will work fine.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote

A ground connection or counterpoise for the dipole/loop
would be benign in the practical sense. You won't need it (unless you
have lightning phobias);

Well said. And most of us who get anywhere near as much rain as Richard
does (in WA) unfortunately have a LOT more lightning to deal with in the
summer. In that case, shield-grounding the coax of a dipole should happen as
soon as the feedline is down at ground-level, and again at the station
entrance/single point ground, where it should connect to a coax
surge/lightning arrestor.

Perhaps the ground of the BalUn can just go to the coax sleeve?

That will work fine.

73's
Richard Clark, KB7QHC

Indeed, matching transformers such as Industrial Communications Engineers
make, insist the metal xfmr case be grounded for safe and proper operation.
I ground long wires on both an I.C.E. xfmr and a current-type Balun,
directly to ground rods that the equipment is mounted on. This is also the
connection point for ground radials for the long wire, if used.

Best regards,

Jack Painter
Virginia Beach, Virginia

On Mon, 14 Mar 2005 16:53:57 -0500, "Jack Painter"
wrote:
And most of us who get anywhere near as much rain as Richard
does (in WA) unfortunately have a LOT more lightning to deal with in the
summer.

Hi Jack,

In all actuality, Seattle sees the least lightning nationwide. If
you drew a line from Seattle to Miami, you would find that the
incidence of lightning grows roughly ten-fold as you progressed along
that line.

73's
Richard Clark, KB7QHC

On Mon, 14 Mar 2005 16:07:50 -0500, clvrmnky
wrote:
Right now I'm running battery only because I have perfectly useful
rechargeables. Anyway, it is giving me a chance to see if the PS adds
any noise. It doesn't appear to.

Hi OM,

That is fortunate. Try not to introduce any grounds such as you
discuss below.

It would seem this is another place where various holy wars have waged
over the years. My survey of the literature indicates that a great many
people don't even consider a dipole of any stripe fed to an unbalance
RX/TX as a "dipole."

Dipole has only one meaning of value: Two Poles. Each pole acts as
the electromotive opposite of the other. Without opposites, no
current flows (and in a sense, a monopole finds its dipolar opposite
in ground).

Isn't this the notion of many of those cheapo plastic baluns one gets to
feed coax to an older TV which would have accepted parallel line?
Well, I suppose these are ostensibly to match impedance, but they are
described as converting balanced to unbalanced connections.

BalUns are so simple that the cheap ones work quite well.

I understand that ground (as a notion) is not an absolute. I have what
I have. I *may* be able to convince my landlord to let me trail a wire
off the balcony to the ground. We'll see.

Don't go there. Introduction of alternate grounds, especially if they
do not conform to code bring the almost certainty of ground loops.
You don't even want to consider the insurance risk. There is probably
no reception advantage over the already available service ground found
at the wall socket. (I am perhaps mistakenly presuming this was for a
receiver only.)

According to what you suggested so far, both sides of my loop can go
directly to my antenna input.

The input and chassis, per accepted terms for both.

Ok, can do. I'll give it a try and see
if things work measurably better.

You may find you are already at the knee of the curve of diminishing
returns. What will pay off is

1. making the antenna connection as remote as possible;
2. using coax;
3. choking that connection;
4. providing for antenna tuning at the radio.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote
"Jack Painter"
wrote:
And most of us who get anywhere near as much rain as Richard
does (in WA) unfortunately have a LOT more lightning to deal with in the
summer.

Hi Jack,

In all actuality, Seattle sees the least lightning nationwide. If
you drew a line from Seattle to Miami, you would find that the
incidence of lightning grows roughly ten-fold as you progressed along
that line.

73's
Richard Clark, KB7QHC

Hi Richard, I knew that, and meant by inference that it was admirable for
someone (you) with so little lightning, to realize it is not a minor-thing
for others.

I might act like my station is bulletproof (because I spent the time and
money to try to make it so), but when you watch that line of a storm
approaching, and lightning is striking every few seconds on a path you can
see coming straight for you, the realization that one is likely to land on
top of you is real, not a phobia, lol. All too often, it does strike one of
the tall pines in my yard, sometimes jumping to non-conductive things like
wooden fences, which it splits on its way to ground.

In Virginia Beach, we get more than half the lightning Miami gets, but
slightly less than half what the 100+ area of West-Central Florida does. It
serves to make summer a lot less fun for those with masts, wires and towers
up in the air!

Best regards,

Jack

On 14/03/2005 5:51 PM, Richard Clark wrote:
On Mon, 14 Mar 2005 16:07:50 -0500, clvrmnky
wrote:

Right now I'm running battery only because I have perfectly useful
rechargeables. Anyway, it is giving me a chance to see if the PS adds
any noise. It doesn't appear to.


Hi OM,

That is fortunate. Try not to introduce any grounds such as you
discuss below.


It would seem this is another place where various holy wars have waged
over the years. My survey of the literature indicates that a great many
people don't even consider a dipole of any stripe fed to an unbalance
RX/TX as a "dipole."


Dipole has only one meaning of value: Two Poles. Each pole acts as
the electromotive opposite of the other. Without opposites, no
current flows (and in a sense, a monopole finds its dipolar opposite
in ground).

I've had an epiphany of sorts, and I think you may be partially to
blame! Well, that and "Basic Electronics" published by the US Navy.

The reason I'm so doggedly trying to get all this is that I'm also
working on getting my amateur radio license. One problem with this is
that I may be conflating "best practises" I'm reading about for TX with
RX purposes. This is the danger of just enough knowledge. I'm
determined to learn how these devices work, and how to best use them.

However, last night I realized that I can think about a RX antenna as an
HF AC current /generator/ running with a small voltage potential (i.e.,
~1 uV), and that my receiver completes this AC circuit.

Then it follows that a longwire needs an RF ground (of some nature) to
"complete" the circuit. Hence, the use of a counterpoise in some
situations. My receiver is one part of an AC circuit that wants some
kind of RF ground to see the voltage potential being generated by the
antenna. Crystal radio sets seem less like magic now.

Of course, grounds for lightning, static or noise attenuation is
related, but not specifically part of the antenna as an AC generator.

So, my "folded dipole" (or, likewise, any doublet) does not rely on
ground to complete this AC circuit, and works relatively well as an AC
generator with a small voltage potential it presents at the receiver
front-end. It follows that all the ground I should need (for good
operation) is a good chassis ground, even if that is only the neutral
side of the wall-wart (is that where it is?). Other issues like ground
loops, reduction of common-mode noise &etc. is a separate issue; these
can *sometimes* be solved by different devices on the antenna system,
but I see now how they could also add problems.

So, when people complain about balance/unbalanced situations, they often
talk about the radiation lobes of a TX antenna being uneven in some
manner they would like to minimize. Perhaps there are gain issues, as
well. I have no idea how my analogy works in this regard with RX
antennas (perhaps my dipole will be slightly "deaf" on a particular axis
if I do not balance/tune it before plugging it into my receiver), but I
can take a baby step and suggest that the various things we can put
between the antenna and the receiver are often RLC circuits meant to
lengthen or shorten the electrical length of the wire. The main intent
is to manipulate the resonance of the antenna for whatever purpose.

I know my explanation has a certain amount of hand-waving and holes, but
it is really helping me understand how the antenna fits into the
receiver as a total system.

The rest of your comments make a lot more sense to me when I think of
things in this manner.

Thanks to everyone in this thread for coaching me in what I hope is the
right direction.

-- cm

On Tue, 15 Mar 2005 12:53:33 -0500, clvrmnky
wrote:
I've had an epiphany of sorts, and I think you may be partially to
blame! Well, that and "Basic Electronics" published by the US Navy.

Hi OM,

I was an Instructor at the Navy's Electronic Technician School at
Treasure Island. Get yourself a copy of Terman's "Electronic and
Radio Engineering" (the 1955 version) to find the level of coursework
that was offered at this school. It is very accessible reading and
noteworthy for being comprehensive without being a sleeping pill.

However, last night I realized that I can think about a RX antenna as an
HF AC current /generator/ running with a small voltage potential (i.e.,
~1 uV), and that my receiver completes this AC circuit.

Good that you picked this up yourself. It is a useful metaphor.

Then it follows that a longwire needs an RF ground (of some nature) to
"complete" the circuit. Hence, the use of a counterpoise in some
situations. My receiver is one part of an AC circuit that wants some
kind of RF ground to see the voltage potential being generated by the
antenna. Crystal radio sets seem less like magic now.

Quite so.

It follows that all the ground I should need (for good
operation) is a good chassis ground, even if that is only the neutral
side of the wall-wart (is that where it is?).

Well, this is getting close to the mystery of your understanding. As
simple as ground is, it is so often taken for granted that many don't
really understand it at all.

As for the Neutral connection of the mains NO THAT IS NOT GROUND!

DO NOT PROCEED FURTHER with any wire work at that service until you
research this completely.

However, as a point of intuition, ground is so tightly coupled to this
wire (at RF) so as to be the missing half of the longwire system.
This is why I commented on the distinction of being completely battery
operated (hence no ground coupling).

Other issues like ground
loops, reduction of common-mode noise &etc. is a separate issue; these
can *sometimes* be solved by different devices on the antenna system,
but I see now how they could also add problems.

This goes again to the common misunderstanding. You won't suffer a
ground loop until it occurs. Solving it will be one of life's
greatest struggles, and the solution, if stumbled upon, will appear to
be one of life's greatest mysteries. Again, battery operation creates
its own bubble of isolation from these issues - however, adding a
charger brings the prospects back into the equation.

So, when people complain about balance/unbalanced situations, ...

Here you get into uncharted waters. Spend some more time here before
you solo again.

73's
Richard Clark, KB7QHC

On 15/03/2005 8:33 PM, Richard Clark wrote:
On Tue, 15 Mar 2005 12:53:33 -0500, clvrmnky
wrote:

[...]

I was an Instructor at the Navy's Electronic Technician School at
Treasure Island. Get yourself a copy of Terman's "Electronic and
Radio Engineering" (the 1955 version) to find the level of coursework
that was offered at this school. It is very accessible reading and
noteworthy for being comprehensive without being a sleeping pill.

I'll look for that title. I'm finding some of the older technical
instruction books very useful.

[...]

It follows that all the ground I should need (for good
operation) is a good chassis ground, even if that is only the neutral
side of the wall-wart (is that where it is?).

Well, this is getting close to the mystery of your understanding. As
simple as ground is, it is so often taken for granted that many don't
really understand it at all.

As for the Neutral connection of the mains NO THAT IS NOT GROUND!

DO NOT PROCEED FURTHER with any wire work at that service until you
research this completely.

Absolutely. I actually have home wiring experience (I don't have my
electrician's ticket, but I could wire my own home, and it would pass
inspection.) I'm surmising that the ground my receiver is seeing (at
least the DC components within it) is the neutral wire. My comment was
more of a rhetorical comment, not a threat to use the white wire on my
AC outlet as ground!

However, as a point of intuition, ground is so tightly coupled to this
wire (at RF) so as to be the missing half of the longwire system.
This is why I commented on the distinction of being completely battery
operated (hence no ground coupling).

Other issues like ground
loops, reduction of common-mode noise &etc. is a separate issue; these
can *sometimes* be solved by different devices on the antenna system,
but I see now how they could also add problems.

This goes again to the common misunderstanding. You won't suffer a
ground loop until it occurs. Solving it will be one of life's
greatest struggles, and the solution, if stumbled upon, will appear to
be one of life's greatest mysteries. Again, battery operation creates
its own bubble of isolation from these issues - however, adding a
charger brings the prospects back into the equation.

Fair enough.

I get a bit of a boost in signal running off the wall-wart, but it is
actually more convenient for me to run off batteries. I end up moving
the receiver around quite a bit. I can pick the big blowtorches and the
relays from Sackville quite nicely off the whip, so I often listen to
them in the kitchen or when doing chores around the house. For "DXing"
I settle in near the door where I've got my antenna experiments going.

This month I'm going to rig up that big loop and see how things change
from the random wire.

"clvrmnky" wrote
On 15/03/2005 8:33 PM, Richard Clark wrote:
As for the Neutral connection of the mains NO THAT IS NOT GROUND!

Absolutely. I actually have home wiring experience (I don't have my
electrician's ticket, but I could wire my own home, and it would pass
inspection.) I'm surmising that the ground my receiver is seeing (at
least the DC components within it) is the neutral wire. My comment was
more of a rhetorical comment, not a threat to use the white wire on my
AC outlet as ground!

Hi OM, it's clear you understand that wal-warts have only two connectors to
AC (hot and neutral), and neutral is bonded to ground at the mains.

My question to Richard (and group) is whether there is any RF or DC link to
ground via a radio's DC-power connection to a wal-wart? I have never
examined the internal components of a sealed wal-wart, only seen the results
of surge voltages from lightning that exploded them and damaged radios they
were connected to. Nothwithstanding the forces of lightning that made that
connection, isn't there isolation from ground when a DC converter is used?

Cheap DC converters can add noise to an electrical system and affect radio
reception, but I didn't think there was any DC coulping across the
transformer wiring, and probably limited if any rf-coupling there either.
Can anyone comment on this?


This goes again to the common misunderstanding. You won't suffer a
ground loop until it occurs. Solving it will be one of life's
greatest struggles, and the solution, if stumbled upon, will appear to
be one of life's greatest mysteries. Again, battery operation creates
its own bubble of isolation from these issues - however, adding a
charger brings the prospects back into the equation.

It's my understanding that ground loops are most common from having serial
v. parallel connections to ground from various equipments. Daisy-chaining a
series of radios to the common ground would thus allow radios to exhibit
feedback through each other instead of only to ground. When a properly
bonded system is connected (each unit indivdually connected to the single
point ground) there is no ground loop. Others often ask what about multiple
bonding-points of the external ground system and it's connection to the AC
mains? Answer: These are not ground loops and are not the cause of equipment
interference from the series-connections of equipments described above.


I get a bit of a boost in signal running off the wall-wart, but it is
actually more convenient for me to run off batteries. I end up moving
the receiver around quite a bit. I can pick the big blowtorches and the
relays from Sackville quite nicely off the whip, so I often listen to
them in the kitchen or when doing chores around the house. For "DXing"
I settle in near the door where I've got my antenna experiments going.


That's interesting OM, as it implies you are seeing a counterpoise effect of
rf-coupling across the windings of the dc transformer, or perhaps just the
secondary side? If a wal-wart helps complete an antenna, it would seem
there may be a design component missing from the antenna somewhere ;-)

Best regards,

Jack
(fmr navy instructor of strategic weapons systems electronics, now a
plug-n-play operator for the uscg)

On 16/03/2005 12:02 PM, Jack Painter wrote:
"clvrmnky" wrote

[...]

I get a bit of a boost in signal running off the wall-wart, but it is
actually more convenient for me to run off batteries. I end up moving
the receiver around quite a bit. I can pick the big blowtorches and the
relays from Sackville quite nicely off the whip, so I often listen to
them in the kitchen or when doing chores around the house. For "DXing"
I settle in near the door where I've got my antenna experiments going.

That's interesting OM, as it implies you are seeing a counterpoise effect of
rf-coupling across the windings of the dc transformer, or perhaps just the
secondary side? If a wal-wart helps complete an antenna, it would seem
there may be a design component missing from the antenna somewhere ;-)

I realized that my nomenclature was wrong. I should have said "bit of a
boost in amplitude" because this is what I'm /really/ hearing. I'm
guessing here that when running of the wall-wart we just have more
available current to draw on for RF and AF amplification, heterodyning
&etc. I have no proof that the signal coming into the set is any
better/stronger or that my antenna is more sensitive or selective.

That is, I don't recall the signal meter changing much when I switch
back and forth between battery and wall-wart. Although, quieter signals
will be uniformly attenuated (along with the noise) slightly when I
switch to battery.

Currently (with a random-wire antenna) the radio seems to not care what
is on the "ground" side. This is hardly scientific, but when I attach a
good number of feet (i.e., more than the length of the antenna) of
copper wire to the ground side of the antenna input (or touch it with my
hand) I get no noticeable change to tuned stations or between-station
noise. I may hear the slightest bit "tick" of noise when my finger
makes first contact with the case of the plug that goes to chassis
ground. Nothing obvious, however.

Jack,

The classic ground loop can occur even when individual components are
perfectly bonded to a single point ground. The "loop" is formed when a
signal cable connects the bonded components together along an alternate
path. There are many proper fixes for this problem, but one popular
quick and dirty fix is to disconnect the bonding by removing the third
pin on the power plugs. Not a good idea, but it happens a lot.

If correcting ground loops was simply a matter of properly bonding the
components to a single point then nobody would ever bother mentioning
ground loops.

73,
Gene
W4SZ

Jack Painter wrote:

[snip]


It's my understanding that ground loops are most common from having serial
v. parallel connections to ground from various equipments. Daisy-chaining a
series of radios to the common ground would thus allow radios to exhibit
feedback through each other instead of only to ground. When a properly
bonded system is connected (each unit indivdually connected to the single
point ground) there is no ground loop. Others often ask what about multiple
bonding-points of the external ground system and it's connection to the AC
mains? Answer: These are not ground loops and are not the cause of equipment
interference from the series-connections of equipments described above.

"clvrmnky" wrote
Currently (with a random-wire antenna) the radio seems to not care what
is on the "ground" side. This is hardly scientific, but when I attach a
good number of feet (i.e., more than the length of the antenna) of
copper wire to the ground side of the antenna input (or touch it with my
hand) I get no noticeable change to tuned stations or between-station
noise. I may hear the slightest bit "tick" of noise when my finger
makes first contact with the case of the plug that goes to chassis
ground. Nothing obvious, however.

that's normal - wait until you discover "the paper clip principle"...

Or, "when a paper clip attached to the back of the radio receives as much as
your just erected antenna", LOL. Stranger things happen, and it helps if you
record in a log what your antenna experiments have yielded. If you use the
S-meter to help relate signal strength (including noise levels), remember to
measure it against at least three frequencies in your intended listening
range (lowest, mid-range, and highest). No antenna treats the whole hf
spectrum the same and you may develop favorite arrangements for particular
listening desires.

Good luck,

Jack Painter
Virginia Beach, Virginia

On Wed, 16 Mar 2005 12:02:48 -0500, "Jack Painter"
wrote:

My question to Richard (and group) is whether there is any RF or DC link to
ground via a radio's DC-power connection to a wal-wart?

Hi Jack,

The simple boding of neutral to ground, as you offered elsewhere,
suits the RF ground path. If there's an isolation transformer, such
as may be found in the common wall wart, you may be assured that the
interwinding capacitance is suitably high enough to overcome any
notion of being isolated at RF. Precision and low noise applications
that demand higher quality isolation between primary and secondary
mandate a faraday shield between them. This shield only insures an RF
path to ground that is optimized for tight coupling - it has no other
purpose.

73's
Richard Clark, KB7QHC

Good points Gene, and thanks for your reply. The AC connections could
certainly be responsible for a ground loop. But it has been my experience
that so few stations actually bond properly that the preponderance of
possibilities would occur foremost with the direct connection from improper
bonding, not the indirect connection from electrical wiring, which usually
has distance and other connections before circling back to the
offending/receiving equipment. All things need to be considered, and is a
good reason for Richard's comment that "Solving it will be one of life's
greatest struggles, and the solution, if stumbled upon, will appear to
be one of life's greatest mysteries." ;-)

I once had a ground loop from a yagi-rotor that resisted all manners of
alternative grounding, wiring, routing, rf-chokes, etc. You either put up
with it or remove it in that case!

If removing the third plug from the power cord isolated a ground loop
problem, then safer alternatives could be accomplished such as an isolated
ground and separate neutral for a particular power supply, as is common in
sensitive computer systems.

Best regards,

Jack

"Gene Fuller" wrote
Jack,

The classic ground loop can occur even when individual components are
perfectly bonded to a single point ground. The "loop" is formed when a
signal cable connects the bonded components together along an alternate
path. There are many proper fixes for this problem, but one popular
quick and dirty fix is to disconnect the bonding by removing the third
pin on the power plugs. Not a good idea, but it happens a lot.

If correcting ground loops was simply a matter of properly bonding the
components to a single point then nobody would ever bother mentioning
ground loops.

73,
Gene
W4SZ

Jack Painter wrote:

[snip]


It's my understanding that ground loops are most common from having
serial
v. parallel connections to ground from various equipments.
Daisy-chaining a
series of radios to the common ground would thus allow radios to exhibit
feedback through each other instead of only to ground. When a properly
bonded system is connected (each unit indivdually connected to the
single
point ground) there is no ground loop. Others often ask what about
multiple
bonding-points of the external ground system and it's connection to the
AC
mains? Answer: These are not ground loops and are not the cause of
equipment
interference from the series-connections of equipments described above.